Piston



Oct. 20, 1936. J. w. ROBERTS APISTON Filed Feb. 20, 1935 AT TORNEY s. mw m J m Patented oei. 2o, 1936 UNITED STATES PATENT orFicE rls'roN .James w. Roberts, Ben nin, Ga. Application February zo, 1935, serial No. 7,409 4 claims.- (ci. sos-15) This invention relates broadly to compression devices, and'more particularly. vlto anew and improved. piston for combustion engines and the like.

5 The conventional internal combustion engine comprises one or more cylinders in which reciprocates a piston or pistons, the space above each piston between the side walls and closed top of the cylinder comprising a combustion chamber,

in which a mixture of fuel (gasoline) and air is compressed and then exploded in such a manner as to drive the piston downwardly, vthereby revolving a crank-shaft to which said piston is connected by means of an intermediate piston l5. rod. Since the piston must reciprocate in the cylinder, and since the combustion chamber must be as nearly air-tight as possible, the problem of sealing the piston with the walls of the cylinder is a very important one, and in fact, the eillciency of a given engine may be said to vary in direct proportion with the effectiveness of the joint between piston and cylinder. For example, as this `seal fails, compression is reduced, with a resulting loss of power and lower gasoline mileage; oil consumption is increased, since the oil in the crank-case now filters through into the combustion chamber and is there burned with the regular fuel mixture; and particles of raw fuel in said chamber are permitted to pass downwardly into the, crankcase, thereby diluting the oil therein and lowering the quality therel oi',- with a result that improper lubrication `is furnished the working parts of the engine` and unnecessary wear then occurs, the result being to shorten the effective life of the machine.

. Various expedients have been resorted to in providing a seal between the piston and cylinder wall, the generally accepted method being to provide the piston with one or more expansible metal 40 rings which t into grooves provided for that purpose around the peripheral walls of the piston, and which by virtue ot their resilient nature tend tov provide 'an effective `joint.. An objection vto piston rings generally, however, lies in the fact that while they may be reasonably effective for the Purpose intended when the engine is new, said rings become worn during the counties reciprocations the piston must makewhen the engine is'in use; and thatthe eifectiveness of so the rings may be further impaired in the course of time by the terrific heat encountered in the motor, which heat tends to distort the metal of ,the rings and otherwise change or modify the desirable characteristics thereof existing when the article is newly installed. A further-consideration lies in the fact that the walls of the cylinders themselves wear away as the machine is used, this situation iinally necessitating the installation of new pistons and new rings if said use continuesv long enough. 5

instant type, a structure that automatically 15 adapts itself to wear lin the walls of' an associated cylinder, in such a manner as to always tightly seal with said Wall regardless ofthe extent of said wear.

A still further object is to provide a piston 20 that automatically seals itself Vagainst loss of power on its down-stroke.

, A still further object is to assemble the packing ring elements at break joints between the bevelled relativelymovable ends of the packing 25 groove so that as the groove is contracted under the compression and power strokes the packing assembly will be forced outwardly as a whole while oiltrapped under the packing in the contracting groove will escape freely from the joint ,o between the head and skirt into the skirt.

Another object isto provide cheapness of construction and simplicity of operation in a device of the instant character. y

Another object is to conserve oil and gasoline 35 through the employment of a device insuring perfect compression within a combustion engine.

Another object is to promote longevity of engines and engine parts by preventing dilution of crank-case' oil, through the use of 4my invention.

These and other objects made apparent throughout the further progress of this specication are accomplished by means of the instant invention. a full and complete understanding of which is made possible by reference to 45 the drawing herein,v in which: v

Fig. 1 is an exploded view in perspective of a device embodying my invention, illustrating the various elements in dissembled form.

Fig'. 2 is a vertical cross-'sectional view taken 50 .through the middle of a piston embodying my Special attention is now directed to the 'upper portion I3 of I0, which is of a smaller diameter than the lower portion I4, 'this being accomplished as by machining a ledge at I5 and from this point cutting away the upper peripheral wall of the piston at a uniform diameter to the upper edge thereof.A It is to be especially noted that the ledge I5 does not form a right angle with the vertical axis of the piston, but rather, that is 'tapers slightly upwardly'from a point I6 on the piston so as to form a somewhat smaller angle with this' imaginary axis, the resulting structure being a sloping ledge between I3 and Il.

A Associated with I0 is a double sealing member comprising an inner expansible band Il slit vertically as at I'Ia, and an outer expansible band I8 having an oblique slit Ila, the inner circumference of I8 seating snugly with the outer circumference of I'I. The lower portions of I'I and I8 are machined at an angle complementary to that ofledge I5, so that when the said double sealing member is in operative position a tightly fitting though expansible joint is provided between said member' and the ledge, it being further contemplated that the outer walls of said sealing member shall lie'in substantially the same vertical plane as the corresponding walls of IL A second expansible sealing member is placed above the first, this element comprising an inner expansible resilient band I9 and an outer band 20, said bands having spacing slots lila. and 20a, and the under sides of said bands being preferably formed straight and atgright angles to their axes so as to seat snugly with a similar construction on the upper sides of II and I8. Attention is directed to the upper sides of I9 and 20, which are sloped at an angle similar to that of the under sides of the lower sealing elements, the purpose of such construction being made clear elsewhere herein.

If desired, in order to prevent the bands from turning in such a manner that the slits of concentric bands register with each other and/or with similar poitions of adjacent bands, said elements may be drilled as at Ilc (Fig. 3) to receive 'a pin ISd, which maintains the bands in prope relative position.

Attention is now directed to the head or cap 2I- -side thereof is hllowed out as at 22 to provide a smoothly seating arrangement with the upper portion Ila of I0. .The outer portion of the underside of 2| is sloped as at Zia' to provide a smooth angular surface that is complementary tothe upper side of I9 and 20 and registers' snugly said ribs may be cast with the cap, or provided in any other suitable manner; which likewise applies to the `construction of the entire device herein, 1 not being concerned with any method of construction, but rather with the structure per se.

Cap 2| may be provided with a series of downwardly extending studs 24, 24a, 2lb, and 24c, which studsare securely anchored at their tops to said cap, and which are of a suilicient length to extend through holes provided for that purpose in a series of engaging bosses 25, 25a, 25h, and 25c, cast on the inside of I0. Tensioning valve springs 26, 26a, 2Gb, and 26e, are passed over the studs on the under side of the bosses, and the ends of `said studs are threaded to receive castellated nuts 21, 21a, 2lb, and 21e, which nuts provide for varying the tension in the springs, and hence the tension with which cap 2| seats with the top of I Il.

When assembled as indicated in Fig. 2, and installed in an engine (not shown), the operation of my piston is as follows: When an explosion occurs in the combustion chamber above 2|, such as to drive the piston downwardly, a force is transmitted to expansible elements I1 and I8 through intermediate bands I9' and 20, such as to tend to. force said elements, and particularly I8 thereof, outwardly, by virtue of the downwardly sloping structureof ledge I5 with which I1 and I8 register. The extentof this expansion will be determined in each instance by the relative gap existing between the peripheral edge of I8 and the inner-wall of the cylinder with which it is associated, but it is apparent that under all operating conditions, and regardless of the increasing wear of the elements, this gap is always completely.

tightly, and eiiiciently closed on the down stroke of the piston, this operating being accomplished automatically by my invention in utilizing the force of the explosion above to effect this result.

On the up or compression stroke of the piston a somewhat similar action occurs in elements I9 and 20, which expansible elements tend to be forced outwardly along the sloping surface provided at 2Ia, this action eiecting a thoroughly eiiicient sealing means and thereby guarantees maximum compression at all times.

-On the piston's suction stroke the packing groove will expand as its bevelled end walls tend to separate and on its power and compression strokes the groove will contract, and any oil trapped in it under the packing assembly will escape through the telescoping joint between piston head and skirt and pass freely and immediately over the narrow t'op edge of the skirt and return to the crank casewithout being held in close clearances where it might carbonize quickly.

Cap 2l and associated springs provide a smoothly functioning compensating and driving element, which by virtue of its connection with the top of I 0 in the manner described herein eilects a sealing action in conjunction with the piston, with attendant benencial results as aforesaid.

While I have described my invention primarily in connection with an internal combustion engine. it is to be noted that I do not intend to thereby limit myself to this use, but on the contrary intend that I shall vbe accorded protection on every conceivable use to which a'piston of the type disclosed by me, can be put. For example, my invention is' of inestimable value when used in anair compressor, a steam engine, or in any device where super compressionisdesirable.

From the foregoingit is apparent that I have u s prising a skirt member carrying the wrist pin disclosed a new and improved piston, which invention makes perfect compression possible, with attendant economic savings as aforesaid. When employed in an internal combustion it saves oll and gasoline by insuring uniformly high quality compression at all times, regardless of the extent of wear of cylinder walls or pistons, and that it prolongs the life of the motor by preventing dilution of crank-case oil, with attendant deterioration of the lubricating qualities thereof. It is further apparent that my device ,is simple and economical in construction, positive in its action, and thoroughly adapted for all intended purposes.

Although a speciiic form of my invention has been described in detail herein, I do not limit myself thereby, since certain changes, omissions, additions, and the like will suggest themselves to anyone skilled in a given art, in adapting my invention to a specic machine; but intend that 4the appended claims shall be accorded abroad construction and a liberal range of equivalents in keeping with my" contribution in this field.

. I claim:

1. An internal combustion engine piston, combearings and having its head end left open and externally reduced to form a packing groove, a head member telescoping over said reduced portion, means including springs to yieldably conneet said head and skirt, an assembly of split packing rings mounted in said packing groove and adapted to hold the head clear of the adjaand a head member telescoping over said reduced cent open end of said skirt, means izo-maintain the packing rings in said assembly in break joint walls.

, 3 relationship, and oppositely bevelled end walls on said head and skirt adapted to engage and expand thie'wholel packingv ring assembly outwardly, whereby oil trapped within the groove may pass into the skirt through the telescoping joint between the head and reduced portion of the skirt, the means for maintaining the rings at break joints being. a. single axially disposed pin which engages all the rings.

3. A' piston comprising a skirt member having wrist pin bearings andan annular head end left open and provided with an-external packing groove, a head member having a iiange which telescopes over the grooved end of said skirt, said head and skirt having reversely bevelled end walls for said groove, means including springs to connect said skirt and head free for relative axial play, and an assembly of packing rings interposed in said groove between said bevelled -shaped-to abut in a plane normal to thepiston axis, and means to maintain the slits in said rings at break joints, said skirt and head aiording a free escapefor oil trapped under the packing ring assembly as the packing grooveis contracted.

4. A piston comprising a cylindrical skirt having wrist pin bearings `and an annular head end rwhich is left open and unobstructed internally and which is externally reduced in diameter to provide a packing groove formed with a bevelled lower end wall, a piston head formed with a reversely bevelled ange adapted to telescope over said reduced skirt end and provide an upper end wall for said packing groove, means including springs' to connect said head and skirt freefor relative axial play, and a ring assembly mounted -in said groove comprising an upper pair' of split nested rings bevelled at one edge and adapted v .to engage the upper groove wall, a similar pair of lower rings bevelled and adaptedto engage the lower groove wall, and an axially disposed key .adapted to engage all rings of the assembly and maintain their slits at break joints as the rings work between their relatively movable groove JAMES w. ROBERTS. 

